Analysis of the early stages of liquid-water-drop explosion by numerical simulation

The early stages of the shock-driven explosion of liquid-water microdrops are studied numerically with a high-resolution discretization of the axisymmetric Euler equations. A level-set based conservative interface-interaction method is extended to allow for phase transition. The method is applied to a configuration that has been investigated in recent experiments [Stan, Nat. Phys. 12, 966 (2016)1745-247310.1038/nphys3779; Stan et al., J. Phys. Chem. Lett. 7, 2055 (2016)1948-718510.1021/acs.jpclett.6b00687]. The presented results show that the numerical model predicts the initial stages of the violent liquid-drop explosion dynamics accurately. Our results indicate that the deformation of the cylindrical vapor cavity within the droplet is not induced by a torus-shaped negative-pressure wave as was implied from the experimental data. We rather find that this torus-shaped wave is a shock wave, and that the observed vapor-cavity deformation is caused by interaction with a negative-pressure region preceding the torus shock. The simulation results show deviations from experimental results at later stages when the drop deformation is dominated by off-center cavitation, i.e., by effects that require extension of the underlying model to take into account generalized nucleation and recondensation.